Mention boot new in preference to lein new

[pesterhazy]

Mention how to create a new project with boot new, as tenzing is based on boot. In my experience boot new works just as well as lein new. Plus it reduces the initial dependendencies from two tools to one tool (boot).

Also adds an explicit section on how to specify options.

[martinklepsch]

Looks good. Wondering if the options should be long-form but probably doesn't matter to much, merging.

[pesterhazy]

⚡️

[martinklepsch]

Thanks 👊